Wireless power transfer systems enable power to be transferred wirelessly from a source to a load. Inductive power transfer is a non-radiative, or near-field, type of wireless power transfer. Inductive power transfer uses an oscillating current passing through a primary coil (i.e., a transmit antenna) of a source to generate an oscillating magnetic near-field that induces currents in a secondary coil (i.e., a receive antenna) of a load. The source includes a power converter having power transistor switches which switch at controllable times to convert power of the source into the oscillating current passing through the primary coil.
Inductive power transfer is performed to wirelessly charge a load, such a traction battery of an electric vehicle, using power from the source. In such wireless electric vehicle charging systems, the transmit antenna of the source is embedded in a “charging” mat and the receive antenna (and an associated rectifier) is embedded in a designated location of the vehicle. The inductive power transfer involves inductive coupling between the antennas. For inductive power transfer to be efficient, the spacing between the antennas must be relatively close within small offset tolerances.
An electric vehicle requires frequent charging of the traction battery. In wired charging connections, an electric vehicle's on-board charger is connected to electric vehicle supply equipment (EVSE), such as a charging station, using a cordset plugged into a vehicle's charging port. A wired control loop between the on-board charger and the EVSE is used to monitor the battery charger output while the cordset is plugged in to the charging port. Upon a detection of any unexpected problems, the control loop may immediately shut down the output from the charging station to protect the traction battery from damage. In wireless charging systems, the control loop is likewise wireless, relying on near-field communication protocols such as WiFi, Bluetooth, etc. to communicate with the power source. Due to its nature, wireless communication is generally slower than wired connections. In the event of a charging error, the source may be relatively slow to respond by shutting down. This delay may cause damage to expensive vehicle batteries and high-power electronics.